1. Field of the Invention
Embodiments of the invention relate to a precursor source canister, such as an ampoule, for providing a vaporized chemical precursor to a processing chamber.
2. Description of the Related Art
Chemical vapor deposition (CVD) and atomic layer deposition (ALD) are techniques for forming materials on a substrate. The material is generally formed by the reaction of vapor phase chemicals on and/or near the surface of the substrate. Typically, CVD and ALD processes involve the delivery of gaseous reactants to the substrate surface where a chemical reaction takes place under temperature and pressure conditions favorable to the thermodynamics of the reaction. The type, composition, deposition rate, and thickness uniformity of the materials that may be formed using CVD or ALD processes are generally limited by the ability to deliver chemical reactants or precursors to the substrate surface.
The chemical precursor within the ampoule or canister is usually in a liquid state during the deposition process. However, the same chemical precursor may be a solid, liquid, or gas at ambient conditions. The chemical precursor typically contained within the ampoule or canister is heated to form a gaseous precursor. The gaseous reactants are typically flowed to a processing chamber having the substrate therein and used to form deposited materials.
Many ampoules and canisters are commercially available to store chemical precursors or to delivery chemical precursors to the processing chamber. However, these ampoules and canisters create challenges. For example, when the level of the chemical precursor is reduced by vaporization within an ampoule, the generation rate of the gaseous reactants decreases accordingly. Moreover, since the flow rate of the gaseous reactants heavily depends on the surface area of the interface between the chemical precursor and the carrier gas the decrease in the precursor level also decreases the interface area, thus lowering the flow rate of the gaseous reactants.
Therefore, there is a need for an ampoule or canister for providing a more constant or substantially constant flow rate of the gaseous reactants while the chemical precursor level decreases during a process.